Herein is disclosed a phase change ink imaging/transfix component and layers thereof, for use in offset printing or ink jet printing apparatuses. In embodiments, the imaging component is responsible for a) accepting an ink image and b) transfer of the ink image (imaging member), or c) transfer and fusing (transfix member) of the developed image to a print medium or copy substrate. The phase change imaging/transfix component can be used in combination with phase change inks such as solid inks. In further embodiments, the conductivity in these surface(s) can be imparted by the addition of either ionic salts, electronically conducting particles, or the like, or mixtures thereof.
Ink jet printing systems using intermediate transfer, transfix or transfuse members are well known, such as that described in U.S. Pat. No. 4,538,156. Generally, the imaging or transfix printing or intermediate transfer member is employed in combination with a printhead. A final receiving surface or print medium is brought into contact with the imaging/transfix printing surface after the image has been placed thereon by the nozzles of the printhead. The image is then transferred and fixed to a final receiving surface.
More specifically, the phase-change ink transfer printing process begins by first applying a thin liquid, such as, for example, silicone oil, to an imaging member surface. The solid or hot melt ink is placed into a heated reservoir where it is maintained in a liquid state. This highly engineered ink is formulated to meet a number of constraints, including low viscosity at jetting temperatures, specific visco-elastic properties at component-to-media transfer temperatures, and high durability at room temperatures. Once within the printhead, the liquid ink flows through manifolds to be ejected from microscopic orifices through use of proprietary piezoelectric transducer (PZT) printhead technology. The duration and amplitude of the electrical pulse applied to the PZT is very accurately controlled so that a repeatable and precise pressure pulse can be applied to the ink, resulting in the proper volume, velocity and trajectory of the droplet. Several rows of jets, for example four rows, can be used, each one with a different color. The individual droplets of ink are jetted onto the liquid layer on the imaging member. The imaging member and liquid layer are held at a specified temperature such that the ink hardens to a ductile visco-elastic state.
After depositing the image, a print medium is heated by feeding it through a preheater and into a nip formed between the imaging member and a pressure member, either or both of which can also be heated. A high durometer synthetic pressure member is placed against the imaging member in order to develop a high-pressure nip. As the imaging member rotates, the heated print medium is pulled through the nip and is pressed against the deposited ink image with the help of a pressure member, thereby transferring the ink to the print medium. The pressure member compresses the print medium and ink together, spreads the ink droplets, and fuses the ink droplets to the print medium. Heat from the preheated print medium heats the ink in the nip, making the ink sufficiently soft and tacky to adhere to the print medium. When the print medium leaves the nip, stripper fingers or other like members, peel it from the printer member and direct it into a media exit path.
To optimize image resolution, the transferred ink drops should spread out to cover a predetermined area, but not so much that image resolution is compromised or lost. The ink drops should not melt during the transfer process. To optimize printed image durability, the ink drops should be pressed into the paper with sufficient pressure to prevent their inadvertent removal by abrasion. Finally, image transfer conditions should be such that nearly all the ink drops are transferred from the imaging member to the print medium. Therefore, it is desirable that the imaging member have the ability to transfer the image to the media sufficiently.
The imaging member is multi-functional. First, the ink jet printhead prints images on the imaging member, and thus, it is an imaging member. Second, after the images are printed on the imaging member, they can then be transfixed or transfused to a final print medium. Therefore, the imaging member provides a transfix or transfuse function, in addition to an imaging function.
In duplex machines, maintenance oils, release oils, release agents, fuser oils, fuser agents, and the like, are normally used in order to provide appropriate transfix function. However it can be difficult to control the amount of release agent on the pressure member and the imaging/transfix member. The oil level on the pressure member, as transferred by contact with the imaging/transfix member or by carryout in an inked portion of the printed image, is a major cause of ghosting and duplex drop out.
Much of duplex print quality in phase change ink printers is driven by oil levels, both on the pressure member and on the imaging member. While many coatings may be oleophobic, they do not have the physical integrity to withstand prolonged printing cycles, or duplex cycling. Therefore, it is desired to provide a composite coating, which combines oleophobic properties with very good physical properties such as toughness and adhesion to the substrate.
Several coatings for the imaging member have been suggested.
U.S. Pat. No. 5,389,958 is an example of an indirect or offset printing architecture that uses phase change ink. The ink is applied to an intermediate transfer surface in molten form, having been melted from its solid form. The ink image solidifies on the liquid intermediate transfer surface by cooling to a malleable solid intermediate state as the drum continues to rotate. When the imaging has been completed, a transfer roller is moved into contact with the drum to form a pressurized transfer nip between the roller and the curved surface of the intermediate transfer surface/drum. A final receiving web, such as a sheet of media, is then fed into the transfer nip and the ink image is transferred to the final receiving web.
U.S. Pat. Nos. 5,777,650; 6,494,570; and 6,113,231 show the application of pressure to ink-jet-printed images. U.S. Pat. Nos. 5,345,863; 5,406,315; 5,793,398; 6,361,230; and 6,485,140 describe continuous-web ink-jet printing systems.
U.S. Pat. No. 5,195,430 discloses a pressure fixing apparatus for ink jet inks having 1) an outer shell of rigid, non-compliant material such as steel, or polymer such as acetal homopolymer or Nylon 6/6, and 2) an underlayer of elastomer material having a hardness of about 30 to 60, or about 50 to 60, which can be polyurethane (VIBRATHANE, or REN:C:O-thane).
U.S. Pat. No. 5,502,476 teaches a pressure roller having a metallic core with elastomer coating such as silicones, urethanes, nitriles, or EPDM, and an intermediate transfer member surface of liquid, which can be water, fluorinated oils, glycol, surfactants, mineral oil, silicone oil, functional oils such as mercapto silicone oils or fluorinated silicone oils or the like, or combinations thereof.
U.S. Pat. No. 5,808,645 discloses a transfer roller having a metallic core with elastomer covering of silicone, urethanes, nitrites, and EPDM.
U.S. Patent Publication No. 20030235838 discloses an offset printing machine having an imaging member with an outer coating that may comprise a polyurethane thermoset.
U.S. Patent Publication No. 20060038869 discloses an offset printing machine having an imaging member with an outer coating that may comprise a polyurethane thermoset.
U.S. Patent Publication No. 20060238586 discloses an offset printing apparatus having a transfix pressure member with a substrate and an outer layer having a polyurethane material, wherein the polyurethane outer layer has a modulus of from about 8 to about 300 Mpa, a thickness of from about 0.3 to about 10 mm, and wherein the pressure exerted at the nip is from about 750 to about 4,000 psi, and wherein the outer layer has a convex crown.
It is desired to provide an imaging/transfix member for use with phase change ink printing machines, including duplex machines and direct-on-paper, direct-on-web, or continuous web machines, which improves the problem of gloss alterations to the image that can be overall or patterned (ghosting), and ink offset to the imaging/transfix roll surface, which can be re-deposited back onto the copy substrate. It is desired that the imaging/transfix roller maintain the functional properties required for roll performance, while satisfying the electrical conductivity or static dissipation requirements. It is also desired that the transfix member, when heated to the operating temperature, be thermally stable. Moreover, it is desired to provide an imaging/transfix roller that is wear-resistant, has consistent mechanical properties under high load, resists adhesion of ink, and is conductive.